1. Field of the Invention
This invention relates to a method and apparatus for thermoforming a pair of integral handles on an all-plastic carton or container, and more particularly, a carton or container used to house milk, orange juice, and similar liquids in order to facilitate the pouring of the contents from the container.
2. Description of the Prior Art
For many years, cartons for milk and similar liquids were formed in part by setting up a preformed paper blank with the bottom of the carton closed and dipping the carton in molten paraffin to seal it. Thereafter, the carton was filled and its top closed.
The wax or paraffin coated carton has been almost entirely supplanted by a heat sealable thermoplastic coated, paperboard carton. The manufacture of the latter carton is different from the wax coated carton in several material respects. Instead of applying the sealing coating after the carton is almost completely formed, the coating of thermoplastic is applied to a paperboard web by extruding it as a thin film onto the paperboard web as one of the earliest steps in the formation of the carton and before any of the other steps are performed such as cutting a blank from the web, scoring and folding it, and the like. After coating, the web is cut into blanks, which are scored and folded into cartons and its bottom structure is sealed by applying heat to the overlapping flaps or panels by which the bottom structure is formed, the heat causing the thermoplastic to flow between adjacent surfaces to seal the same. Such cartons are usually formed with a gable top, or one which when unfolded forms an integral pouring spout along one entire sidewall. The top is folded and sealed along a ridge line by heating the thermoplastic coating.
Such carton details, per se, and the manner of assembly thereof are fully disclosed in U.S. Pat. Nos. 3,120,335 and 3,116,002, which disclosures are incorporated herein by reference. As shown in detail in these patents, the carton bottom structure is formed by folding panels transversely across the bottom of the carton, the panels being folded on score lines. The bottom structure is completed by applying heat and pressure to the panels which are folded upon one another. The thermoplastic which has been applied to the paperboard fuses during the application of heat and pressure to form a sealed bottom structure. The top structure is also folded about score lines and adjacent surfaces fused to seal the liquid contents in the carton. It can be opened in such a way as to form the pouring spout. After the carton bottom structure has been formed, the carton is filled with milk or other liquid and then the top seal is formed by folding the gable top panels on score lines and fusing adjacent surfaces.
More recently, in lieu of paperboard, such gable top containers have been formed from all-plastic material, as disclosed specifically in U.S. Pat. No. 4,126,262. As disclosed, a thermoplastic core of polyolefin, polyvinyl chloride, polystyrene, polyvinyl acetate and copolymers thereof is sandwiched between outer layers of low density polyethylene. Such material can be scored, cut and folded in the same manner as the thermoplastic coated paperboard, but does not exhibit the problems caused by wetting of the paperboard, such as pinhole leaks, deformation of shape, and the like, discussed more fully in the patent which is also incorporated herein by reference.
Such cartons are somewhat inconvenient to handle, especially in the larger gallon sizes which have become more desirable to the consumer because of decreased cost in buying milk or other food liquids in quantity. Not only are such filled cartons heavy to carry, but upon opening of the gable top to pour the contents, the large bulk of the side of the carton precludes the side of the carton from being readily grasped to tilt the carton.
Accordingly, users have resorted to pivotable or tiltable racks which support the carton while pouring the contents, leading to increased cost and bother in their use.
An alternative is to provide an integral handle on the gable top of the carton. However, this requires additional material to be utilized in forming the blank, which is uneconomical, and presents other manufacturing problems related to effecting a proper seal of the gable top so as to be able to unfold the same to provide a pouring spout for the container. The problems associated with providing such a construction are detailed in copending application Ser. No. 955,809, filed Oct. 27, 1978, now U.S. Pat. No. 4,214,697 assigned to the same assignee as the present application, which is also incorporated herein by reference. As indicated in the copending application, one serious problem in manufacturing a blank with an integral handle secured to the gable top is the manner in which the blanks are laid out and cut from a web, without undue waste.
Because of the difficulty in providing an integral carrying handle on a gable top container, many container manufacturers have discarded the use of thermoplastic coated, paperboard or all-plastic, laminated type containers and opted to blow-mold a container, particularly in the one-gallon size or larger, because it can readily be provided with an integral handle structure to carry the container and to hold the container while pouring its contents.